Vehicle would not start. 48v battery light came on. Waited 15 minutes, vehicle started, drove to dealership who did diagnosis. Battery replacement required $1800 + $1200 labor. 2020 vehicle with 61K miles. Bought certified vehicle from MBZ dealership, added a MBZ 3 year or 100K mile extended warranty but this battery is considered a wear and tear item not covered. That would be fine except for…
2020 Mercedes-Benz GLS-Class electrical problems
severe 17 complaints filed with NHTSA · avg repair $850 · see electrical across all vehicles →
Complaints
17
Recalls
0
Avg fix
$850
1crash
1fire
When does it fail?
Of the 17 electrical complaints filed for the 2020 Mercedes-Benz GLS-Class, here's the actual mileage breakdown — failures cluster heaviest at 0-25,000 mi.
0-25k
25-50k
50-75k
75-100k
100-125k
125-150k
150k+
Each bar shows the share of total complaints filed at that mileage range. Peak failure window highlighted. Some owners report problems earlier; some make it well past 150,000 miles symptom-free. Maintenance habits and driving conditions shift the curve as much as mileage alone.
What stands out
Of the 4 model years of Mercedes-Benz GLS-Class we track for electrical problems, this one carries the most owner complaints on file — 17.
The failure pattern owners describe
The 2020 GLS-Class electrical system exhibits multiple critical failure modes. The 48V battery system fails unexpectedly, causing abrupt engine shutdown mid-drive—on freeways, in intersections, at highway speeds—with warning lights illuminating but zero diagnostic codes stored. Owners report dealers cannot reproduce or identify the cause, returning vehicles unchanged. Multiple owners experienced repeat failures months apart. One owner's burnt 48V cables required $5,804.56 out-of-pocket before Recall 24V207 was issued; the manufacturer offered only $337 in reimbursement.
The engine wiring harness insulation deteriorates prematurely, exposing wires and enabling short circuits that trigger check engine lights and potential power loss. One owner had harness replacement quoted at $5,009.99.
Moisture intrusion is widespread. A bad heating/cooling hose or poor sealing allows water into the cabin, flooding electronics and disabling the MBUX system ($8,350 repair), rearview camera, and main electrical control modules ($4,255 repair). Even a routine car wash can trigger cascading system failures. Dealerships cannot provide permanent fixes.
Assembly defects include ground connections filled with paint during manufacturing, causing 48V warnings and sudden stalling. Dashboard and infotainment screens fail intermittently or completely, leaving drivers without speedometer, fuel, or temperature readings. One HVAC system emits persistent mold smell despite repeated service attempts. Warranty coverage is spotty, and dealers often withhold full diagnostics.
Same Mercedes-Benz GLS-Class electrical reports on nearby years: 2021
Failure modes owners describe
48V Battery System Failure
The 48-volt electrical system fails suddenly while driving, causing the engine to shut off, loss of power steering assist, and inability to accelerate. The battery warning light and check engine light illuminate, but no diagnostic codes are stored in the vehicle's system memory.
When: Various: 5K–61K miles; one incident at ~4100 miles on low-mileage vehicle; repeated failures on same vehicles after several months
Symptoms owners cite: Engine abruptly stalls while driving; Loss of power and acceleration; Vehicle coasts to stop; 48V battery warning and check engine light illuminate; No error codes stored despite warning lights; Difficulty restarting or limp-home mode with overheating warnings
Codes mentioned: P0000 (implied—no codes stored despite warnings)
Repairs/costs cited: Battery replacement: $1,800 parts + $1,200 labor (one owner); dealership unable to locate root cause in multiple instances; one owner's repair involved burnt-out 48V battery cables, replaced at $5,804.56 out-of-warranty
Recalls/TSBs owners mention: Recall 24V207 (2024040002) issued for 48V battery connection misconnection risk; recall reimbursement offered only $337.08 for connection check, not full repair cost incurred pre-recall; dealership service reports conclude root cause cannot be determined
Engine Wiring Harness Degradation
The main engine wiring harness insulation deteriorates, exposing wires and allowing them to contact each other. In some cases, plastic casing disintegrates from environmental exposure. This generates intermittent electrical faults and poses risk of short circuits, power loss, and engine stalling.
When: 5 years old with ~4,000–100,000+ miles; one case identified during routine service at 5 years old
Symptoms owners cite: Intermittent check engine lights; Exposed wires contacting each other; Electrical fault codes; Loss of power; Engine stalling
Codes mentioned: Various electrical fault codes (exact codes not specified in narratives)
Repairs/costs cited: Harness replacement quoted at $5,009.99; one owner found plastic casing had disintegrated; dealership confirmed material durability issue unrelated to external damage
Recalls/TSBs owners mention: One dealership noted similar harness concerns observed on other M256-equipped vehicles but no formal recall or TSB mentioned
Moisture Intrusion into Electrical Systems
Moisture enters the cabin or electrical enclosures due to faulty heating/cooling hose routing or inadequate sealing during assembly. Water floods electronics including the MBUX infotainment system and main electrical control modules, causing widespread system failure.
When: Varies; one incident during routine garage backing-out; one incident triggered by routine car wash; one incident from water drainage on floor mats
Symptoms owners cite: Multiple system failures after moisture exposure; Vehicle electrical control system failure; Vehicle will not turn off; MBUX infotainment system shuts down; Camera view restricted warnings; Adaptive highbeam assist unavailable; Loss of rearview visibility system function
Codes mentioned: Camera view restricted, Adaptive highbeam assist currently unavailable
Repairs/costs cited: MBUX repair: $8,350; general electrical control system repair: $4,255.15 (not covered under warranty); dealership unable to provide long-term fix and recommended non-existent part
Recalls/TSBs owners mention: One owner noted existence of recall for similar moisture-related electrical control system damage on other GLS450 models; no formal manufacturer guidance or retrofit program mentioned in narratives
Electrical Assembly Defects (Paint-Filled Ground Connections)
During manufacturing, paint fills electrical grounding connections between the 48V system and vehicle chassis. This creates high-resistance ground faults that trigger rapid-fire 48V warnings and sudden power loss.
When: Occurs early in vehicle operation; one owner experienced at 25–30 mph on residential street
Symptoms owners cite: Series of 48V electrical system warnings displayed in rapid succession; Vehicle loses power; Engine shuts off; Vehicle glides to stop
Codes mentioned: 48V electrical system warnings (specific codes not detailed)
Repairs/costs cited: Issue traced to paint-filled grounding connections during assembly; repair involved cleaning/replacing ground connections
Dashboard/Infotainment Display Failures
The instrument cluster and MBUX infotainment screens fail intermittently or completely, leaving the driver without speedometer, fuel gauge, temperature, RPM, or navigation display. Screen may blank without warning and restart unpredictably.
When: Intermittent failures; one instance after blank-screen event triggered subsequent check engine light; recurring over 7-month period
Symptoms owners cite: Instrument cluster screen goes blank; Speedometer, fuel gauge, temperature, and RPM displays unavailable; MBUX infotainment system shuts down or freezes; No warning lights or messages prior to failure; Screen returns intermittently after restart; Check engine light appears after restart
Codes mentioned: Check engine light (no specific code provided)
Repairs/costs cited: One vehicle undergoing Mercedes diagnostics; dealership unable to reproduce issue and unable to offer solution; multiple dealer attempts across different dealerships failed to resolve
Recalls/TSBs owners mention: One vehicle assessed as "Certified Pre-Owned" with undisclosed "Special Procurement" status; 200-day EIS (Electronic Information System) remediation attempted at one dealer without success; dealers withholding machine-level XENTRY diagnostics
HVAC Mold Contamination
The AC vent system distributes mold smell throughout the cabin. Multiple service attempts fail to resolve the issue, suggesting systemic contamination or design flaw in the HVAC system.
When: Persistent issue over multiple service visits
Symptoms owners cite: Mold smell emanating from AC vents; Odor present during AC operation
Recalls/TSBs owners mention: Multiple service attempts at dealership failed to resolve; owner reports same issue on family GLE model, also unresolved at dealership
Synthesized from 17 NHTSA owner complaints — unverified consumer allegations, summarized for patterns. The verbatim filings appear below.
What owners are reporting 9 most recent
The vehicle warnign system displayed "48v Malfunction." Vehicke lost all acceleration in the middle of the highway. The vehicle was just returned3 days ago after undergoing a state inspection at the MB dealership. In looking at the issue on line this appears to be a known problem to Mercedes. They are even facing a class action lawsuit for it in the same model year GLE, which is based on many…
Upon starting the car, the screen of the 2020 Mercedes Benz GLS 450 remained blank. This includes the portion of the dashboard that reads speedometer, gas, temperature, RPM. The engine was running and truck could still be driven. The vehicle is available for inspection upon request. This is a major safety issue as the driver does not have visibility to the dashboard with all it's important…
I have noticed a significant issue with the AC vent system of my Mercedes GLS 450. The vents seem to be distributing mold smell already took my vehicle multiple times to park place Mercedes in Dallas and they performed service but the issue is persistent. I have taken the vehicle to my local Mercedes service center, where they attempted to address the issue. However, despite their efforts, the…
While driving the vehicle, a series of electrical system warnings were displayed in rapid succession. Shortly thereafter, the vehicle lost power, the engine shut off, and the vehicle began to glide. This incident occurred on a residential street while the vehicle was travelling at 25-30 MPH. The warnings were specific to the 48v electrical system. The vehicle was operable after the incident and…
While driving on the New Jersey Turnpike on November 17, 2023, a burning smell was noticed inside the car. The smell lasted about an hour. No smoke was present and the car continued to operate. While concerned, I assumed it was environmental and outside the car. On November 25, 2023 my car threw a 48V battery warning and forcibly shut off. We were not on a highway at the time and were able…
The vehicle issued a “48v battery malfunction” and the car warned me not to drive the vehicle under any circumstance. This was while driving at 55 mph on a country road. The dealer I bought the car from had 3 other cars brought in for the same issue. The dealer my car was towed to said they just had one with the same issue come in. Based on my reading, this is a serious issue and it appears that…
AMENDMENT TO ACTIVE CASE 11723015. CRITICAL AIRBAG & SAFETY DEFECTS. This files a safety defect amendment to open case 11723015. Diagnostic scans confirm central data bus network collapse on VIN [XXX] has migrated into safety-critical occupant restraint and visibility modules, violating 49 U.S.C. § 30118. I. AIRBAG & RESTRAINT HAZARDS Scans from [XXX], document active faults: DTC U042782:…
While driving, vehicle has abruptly stopped/engine turned off causing car to not accelerate and come to a stop. One instance was on a busy freeway, causing our family to pull off the interstate with nearly no curb, risking rear-end collision due to the abrupt stalling of the vehicle. In this instance, the 48 volt battery failure warning, engine overheat warning, engine light warning came on. When…
Had electrical trouble with your 2020 Mercedes-Benz GLS-Class?
File a complaint with NHTSA → It's free, official, and how every report above got here — owner filings are the federal safety record this page is built on.
Common questions
How serious is the electrical problem on the 2020 Mercedes-Benz GLS-Class?
It's a meaningful issue. 17 complaints have been filed and the failure mode causes operational problems for owners. Repairs average $850.
At what mileage does the electrical typically fail?
Based on the 17 complaints filed, electrical issues most often appear around 6,550 miles. Some report problems earlier; some make it well past 150,000 with no symptoms. Maintenance habits matter — vehicles that received timely fluid services and were not regularly overworked tend to last longer.
What does it cost to fix?
Independent shops typically charge around $850 for electrical repairs on this vehicle. Dealer pricing tends to run 20-40% higher. The exact figure depends on the specific failure mode, parts availability, and your local labor rates. If you're outside factory warranty, an extended service contract often covers this category.
Are there any recalls related to electrical?
No active recalls currently cover electrical issues on this vehicle. The complaints filed represent owner-reported failures that haven't risen to the level of a manufacturer-issued recall — but they're still worth knowing about before you buy or budget for repairs.
Related
Complaint and recall data sourced from the National Highway Traffic Safety Administration (NHTSA)
public records database. Verify the raw federal record at
nhtsa.gov/vehicle/2020/Mercedes-Benz/GLS-Class.
Severity ratings are derived from reported crashes, fires, injuries, and fatalities. Repair cost estimates are
independent-shop national averages and may differ in your area. Some links on this page are affiliate links.